Apparatus for controlling coating width

Abstract

An apparatus for dispensing a fluid onto a moving substrate is disclosed. In one embodiment, the apparatus is a die comprising a die body having a cavity therein, wherein the cavity is in fluid communication with an applicator slot. The die is then oriented such that the applicator slot is positioned so as to dispense the fluid onto the moving substrate. The fluid is introduced into the die cavity such that the fluid is dispensed onto the moving substrate through the applicator slot. At least one end of the slot includes means for preventing lateral widening of the dispensed fluid. In another embodiment, means are disposed at both ends of the applicator slot. The apparatus is particularly useful when the capillary number characteristic for dispensing the fluid onto the moving substrate is less than 0.5.

1. A coating die for dispensing fluid onto a moving substrate at a capillary number, the coating die comprising:
 a die body including a first die portion, a shim and a second die portion in combination defining a cavity therein, wherein the cavity is in fluid communication with an applicator slot having lateral edges facing and extending across the width of the substrate upon which the fluid flowing through and from the applicator slot is dispensed upon; 
 preventing means for preventing widening of the dispensed fluid laterally of the applicator slot arranged in lateral edges of the die portions and in the lateral edges of the shim defining the applicator slot when the capillary number of the dispensed fluid is in a range up to about 0.5, wherein the preventing means comprises a notch arranged in the lateral edges of the die portions and in the lateral edges of the shim defining the applicator slot, and an inlay positioned within each said notch. 
 
   
   
     2. The coating die according to  claim 1 , wherein each inlay further comprises a region of low surface energy material. 
   
   
     3. The coating die according to  claim 2 , wherein the low surface energy material is selected from the group consisting of polytetrafluoroethylene and acetal polyoxymethylene. 
   
   
     4. The coating die according to  claim 2 , wherein the region of low surface energy material comprises a material that is poorly wetted by the dispensed fluid whereby the low surface energy material used for the inlay has a larger static contact angle with the dispensed fluid than a material used for the die body. 
   
   
     5. The coating die according to  claim 4 , wherein the dispensed fluid is water-based and wherein the material that is poorly wetted by the dispensed fluid is a hydrophobic material. 
   
   
     6. The coating die according to  claim 5 , wherein the hydrophobic material comprises a layer of hydrophobic substrate and a layer of adhesive. 
   
   
     7. The coating die according to  claim 1 , wherein the die body is coated with a material that is preferentially wetted by the dispensed fluid. 
   
   
     8. The coating die according to  claim 1 , wherein each inlay comprises a low surface energy material selected from the group consisting of polytetrafluoroethylene, acetal polyoxymethylene, a fluoropolymer derived from vinyl fluoride (VF), a fluoropolymer derived from perfluoroalkylvinylether (PAVE), a fluoropolymer derived from 2,2-Bistrifluoromethyl-4,Sdifuoro-1,3-dioxole (PDD), a fluoropolymer derived from vinylidene fluoride (VDF), a fluoropolymer derived from hexafluoropropylene (HFP), a fluoropolymer derived from chlorotrifluoroethylene (CTFE); fluorinated ethylene propylene, polyvinyl fluoride, polyethylene copolymer, and silicone. 
   
   
     9. The coating die according to  claim 1 , wherein the cavity provides the fluid to the applicator slot and wherein the capillary number of the ispensed fluid flowing from the applicator slot and onto the moving substrate is no greater than 0.01.